Norethindrone, which the three chemists developed in 1951, at first was used as a fertility treatment, only demonstrating its effectiveness for birth control after five years of trials, according to The New York Times. Rosenkranz’s team also achieved the first practical synthesis of cortisone, in 1951, according to The Times.

Rosenkranz studied organic chemistry in Switzerland, earning his doctorate in 1940 before immigrating to Cuba. After World War II he became the research director of the Syntex Corp., a pharmaceutical lab in Mexico. He became a Mexican citizen in 1949.

Rosenkranz became chief executive and chairman of Syntex, which grew into a diversified international pharmaceutical and biotechnology company, retiring in 1981.

He wrote hundreds of articles and scientific papers and was named in 150 patents.

Rosenkranz was a world-class bridge player and won a dozen North American championships. He contributed to bidding theory and invented the Rosenkranz double and Rosenkranz redouble. He also wrote 15 books on bridge.

In July 1984, Rosenkranz’s wife, Edith, one of Mexico’s top players, was kidnapped at gunpoint at the summer North American Bridge Championships in Washington, DC, and ransomed for $1 million. The FBI captured the kidnappers and the money was returned.

Rosenkranz is survived by his wife and two of his three sons, and nine grandchildren.

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